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Small diesel truck - at last
Murf, you mentioned earlier in the thread that you have often demonstrated that it is cheaper to run premium gas than regular. I'm curious what factors you considered in that analysis.
I ran a couple of tankfuls of premium through my Tacoma again. The truck seemed to run just a tiny bit stronger but the mileage actually dropped by about 0.5 mpg with no change in driving habits (still mostly highway driving with cruise set to 62). Comparisons were both of Chevron E10 regular vs. E10 "Supreme" from the same station. Premium is about 8% more expensive so it doesn't seem like a cost effective choice. Then again, when it comes to mileage nothing on this truck seems to follow conventional wisdom.
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Small diesel truck - at last
KW, even under the strictest laboratory conditions it's impossible to determine mileage. Add to your conditions of tire rolling resistance, tire air pressure which varies with temp, moisture content (the air not yours  ), ambient temp which affects everything from fluid viscosity to fuel mixture, wind drag, cross winds, wind velocity, quality and age of fuel even if from station, even the temp of the fuel. Even how much the vehicle weighs and its load--you, tools, and especially fuel content. We we did automotive testing we used a certified slab of steel that weighed 250 lb. for consistency (this wasn't for mileage but crash testing).
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Small diesel truck - at last
Ken, you're right, nothing on that truck seems to fit conventional wisdom.
It could be that the Toyota ECM has been 'de-tuned' already to take into account for the E10 fuel.
I must say though that on none of the samples I took between here & Florida on several trips did I encounter any Ethanol in premium fuels. The way the legislation is worded the Ethanol content is a requirement that is based on a percentage of total fuel sold, so if they can get enough Ethanol into the system in regular and mid-grade they don't need to add it to premium and most aren't.
As for the economy of it, here's how it works (in my particular case), my SUV (mid-sized with a 5.0 liter V8) gets a pretty consistent 18 mpg on regular gas, on premium it gets a an also consistent 21 mpg on premium.
That's a 16.7% increase in mileage, as you pointed out, the difference in price per gallon is almost always under 10%. When I brew my own premium by using additives, the cost difference is about 2% per gallon, but I'm still getting Ethanol.
The part I find hard to believe though is that your truck actually got worse mileage on better fuel, it just doesn't make sense from any angle. If nothing else you were putting more BTU's (energy) per gallon through the truck, so it should have gone further on a gallon all things being equal.
Best of luck.
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Small diesel truck - at last
I'll have to double check the E10 in premium. The pump sticker says E10 on it but I ASSumed it was in all the fuels and not just in regular.
On the off chance that the ECU takes a long time to adjust to the new fuel I'll try it for another couple of tanks.
EW, sure it's possible to compute mileage, it's just not possible to do a pure apples-to-apples comparison. After all, it stands to reason that the driver gets lighter with each passing rest stop and heavier at each drive thru 
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Small diesel truck - at last
OK, you guys want to split hairs on the fuel mileage thing?
There use to be an old guy around town who was a bit wacko anyhow, but he wouldn't fill the gas tank in his car beyond half full. He said he wasn't going to burn gas to haul an extra ten gallons of gas around that he didn't need. I think he weighed around three hundred but he didn't leave part of himself at home, he took all of himself along.
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Small diesel truck - at last
Ken, there's a down 'n' dirty way to get your trucks ECU to 'relearn' the new fuel.
Pull off your positive battery terminal, wait ~5 seconds, then touch it to the negative lead for a second. This will clear all stored data, including 'soft' error codes by discharging the memory. It will be then reset to factory defaults.
Just be sure you've got straight premium (not part regular) gas in the tank and fuel lines. Then drive it the way you normally drive. It may take a while for the truck to relearn your driving style and conditions, but it will happen.
Frank, we had a local fella up here was much the same way, except it was $20 gas and the tailgate always down. Everyone laughed about it because his wife probably weighed nearly what the truck did and she was always with him!
Best of luck.
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Small diesel truck - at last
Ken, while you can compute mileage for a given set of factors and circumstances, because those factors change--and the will--you can't do and apples to apples comparison. And these mileage figures are averages over time and distance. The longer the distance the chances of apples to apples numbers being the same or close are greater.
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Small diesel truck - at last
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Ken, while you can compute mileage for a given set of factors and circumstances, because those factors change--and the will--you can't do and apples to apples comparison. And these mileage figures are averages over time and distance. The longer the distance the chances of apples to apples numbers being the same or close are greater.
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True. The standard deviation of my results is typically ~0.5 mpg so the numbers are all pretty close. It helps because I drive the same route every day and use cruise control. But if I had a big burger the night before I can count on the mileage going down a blip
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Small diesel truck - at last
My wife's Toyot has mileage computer and it is very interesting to see what changes it. She picked up her sister one day and after driving I think less than a mile it dropped her mileage by a good bit. They both laughed at that for a while.
So Ken, is it possible there is an issue with the engine it self that could be causing the drop in mileage? Are you 100% sure the overdrive (auto correct) is working?
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My wife's Toyot has mileage computer and it is very interesting to see what changes it. She picked up her sister one day and after driving I think less than a mile it dropped her mileage by a good bit. They both laughed at that for a while. So Ken, is it possible there is an issue with the engine it self that could be causing the drop in mileage? Are you 100% sure the overdrive (auto correct) is working?
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I don't *know* that there isn't something wrong but the mileage is pretty typical for this truck. Others are reporting the same numbers. That said, I was going to have the door weatherstripping replaced so I'll ask them about the mileage and show them the log.
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